Stator of heat dissipation fan

ABSTRACT

A stator includes a stator core, two insulation frames, and a plurality of coils. The stator core includes a plurality of yokes stacked one on the other along an axial direction of the stator core. The stator core has a larger outer size at one end thereof than the other end thereof. The insulation frames respectively cover the one end and the other end of the stator core. Each coils wounds around the insulation frames and corresponding portions of the stack of yoke. Each of the yokes includes an annular plate and a plurality of arms extending outwardly from an outer periphery of the annular plate, outer edges of the arms of each yoke are located on a same imaginary circle which has a common center with the annular plate, and diameters of the imaginary circles of the yokes are different from each other.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a divisional application of patentapplication Ser. No. 13/278099, filed on Oct. 20, 2011, entitled “HEATDISSIPATION FAN AND STATOR THEREOF”, assigned to the same assignee,which is based on and claims priority from China Patent Application No.201110152299.9, filed in China on Jun. 8, 2011, and disclosures of bothrelated applications are incorporated herein by reference in theirentireties.

FIELD

The subject matter herein genearlly relates to electronic devicecooling, and particularly to a heat dissipation fan providing stablerotation of a rotor thereof.

BACKGROUND

With the continuing development of electronics technology, electronicpackages such as CPUs (central processing units) employed in electronicdevices are generating more and more heat. The heat requires immediatedissipation in order that the CPU and the electronic device can continueto operate stably. A heat dissipation fan is commonly used incombination with a heat sink for cooling the CPU.

A conventional heat dissipation fan includes a stator, and a rotorhaving a hub with a plurality of blades extending from the hub. Thestator establishes an alternating magnetic field interacting with amagnetic field of the rotor to drive the rotor to rotate. Thus therotation of the blades generates a forced airflow, for cooling the CPU.The stator includes a bearing defining a bearing hole therein. The rotorhas a shaft extending into the bearing hole and is thus rotatablysupported by the bearing.

However, during rotation of the rotor, the rotating blades generate anexternal air pressure which pulls the rotor to move upwardly along anaxial direction away from the stator. When this happens, the rotor issaid to be in a “floating” condition. The floating rotor is inclined togenerate noise, which may be annoying or even unacceptable.

What is desired, therefore, is a heat dissipation fan which can overcomethe above-described shortcomings

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations of the present technology will now be described, by wayof example only, with reference to the attached figures, wherein:

FIG. 1 is an isometric, assembled view of a heat dissipation fanaccording to an exemplary embodiment of the present disclosure.

FIG. 2 is an exploded view of the heat dissipation fan of FIG. 1.

FIG. 3 is similar to FIG. 2, but showing the exploded heat dissipationfan inverted.

FIG. 4 is a cross-section of the heat dissipation fan of FIG. 1, takenalong line IV-IV thereof

DETAILED DESCRIPTION

It will be appreciated that for simplicity and clarity of illustration,where appropriate, reference numerals have been repeated among thedifferent figures to indicate corresponding or analogous elements. Inaddition, numerous specific details are set forth in order to provide athorough understanding of the embodiments described herein. However, itwill be understood by those of ordinary skill in the art that theembodiments described herein can be practiced without these specificdetails. In other instances, methods, procedures and components have notbeen described in detail so as not to obscure the related relevantfeature being described. Also, the description is not to be consideredas limiting the scope of the embodiments described herein. The drawingsare not necessarily to scale and the proportions of certain parts havebeen exaggerated to better illustrate details and features of thepresent disclosure.

Several definitions that apply throughout this disclosure will now bepresented.

The term “substantially” is defined to be essentially conforming to theparticular dimension, shape or other word that substantially modifies,such that the component need not be exact. For example, substantiallycylindrical means that the object resembles a cylinder, but can have oneor more deviations from a true cylinder. The term “comprising,” whenutilized, means “including, but not necessarily limited to”; itspecifically indicates open-ended inclusion or membership in theso-described combination, group, series and the like.

The present disclosure is described in relation to a heat dissipationfan.

FIG. 1 illustrates a heat dissipation fan includes a housing 10. Thehousing 10 is generally in the form of a hollow rectangular frame, andincludes a top wall 11, a bottom wall 12 parallel to and spaced from thetop wall 11, and an annular side wall 13 connected between the top wall11 and the bottom wall 12. An air inlet 40 is defined in a centralportion of the top wall 11. An air outlet 50 aligned with the air inlet40 is defined in a central portion of the bottom wall 12.

FIGS. 2 and 3 illustrate two exploded views of the heat dissipation fanin inverted directions respectively. The housing 10 also includes a base121 located at a center of the air outlet 50, a central tube 123extending upward from the base 121, and a plurality of ribs 122extending radially from an outer periphery of the base 121 to connect aninner periphery of the bottom wall 12. The central tube 123 defines acentral hole 124 therein, and thus includes an open top end. The centralhole 124 extends along an axial direction of the central tube 123 forreceiving a bearing 14 therein.

The heat dissipation fan also includes a rotor 30 and a stator 20. Therotor 30 is rotatable about the stator 20. The stator 20 includes astator core 22, a plurality of coils 24 wound on the stator core 22, apair of insulation frames 26, and a PCB (printed circuit board) 28connected to the coils 24 electrically. In this embodiment, there arefour coils 24.

FIG. 4 is a cross-section of the heat dissipation fan, and referringalso to FIG. 3, the stator core 22 is made of metallic material, andincludes layered yokes 221 stacked along a bottom to top directionthereof. Referring back to FIG. 2, each of the yokes 221 includes anannular plate 223 and a plurality of T-shaped arms 224 extendingoutwardly from an outer periphery of the annular plate 223. In thepresent embodiment, there are four arms 224, which are equally spacedfrom each other along a circumference direction of the annular plate223. Inner diameters of the annular plates 223 of the yokes 221 aresubstantially the same. Outer edges of the arms 224 of each yoke 221 arelocated on a same imaginary circle, which has a common center with theannular plate 223. A diameter of the imaginary circle is a diameter ofthe yoke 221. The diameters of the yokes 221 are different from eachother.

More specifically, the diameters of the yokes 221 gradually decreasefrom a bottommost yoke 221 to a topmost yoke 221 along a stackingdirection thereof. Accordingly, when the yokes 221 are stacked togetherto form the stator core 22, a cylindrical receiving space 220 is definedin a central portion of the stator core 22 cooperatively by inner edgesof the annular plates 223 of the yokes 221; and the outer edges of thearms 224 cooperatively define a tapered (frustoconical) outer surface222. The receiving space 220 is configured for receiving the centraltube 123 therein. A diameter of the tapered outer surface 222 graduallydecreases from a bottom end of the stator core 22 to a top end of thestator core 22. That is, an outer size of the stator core 22 decreasesgradually along an axial direction from the bottom end to the top endthereof.

The insulation frames 26 are mounted to top and bottom ends of thestator core 22, respectively. Each insulation frame 26 includes anannular portion 262 and a plurality of claws 264 extending outwardly andradially from an outer periphery of the annular portion 262. The annularportion 262 corresponds to the annular plates 223 of the yokes 221, andthe claws 264 correspond to the arms 224 of the yokes 221. Thus thereare four claws 264, which are equally spaced from each other along acircumference direction of the annular portion 262. The coils 24 windaround the claws 264 of the insulation frames 26 and correspondingportions of the arms 224 to establish an alternating magnetic field inoperation of the heat dissipation fan. The insulation frames 26 spacethe coils 24 from the stator core 22, thereby preventing the coils 24from coming into electrical contact with the stator core 22. The PCB 28with electronic components mounted thereon is electrically connected tothe coils 24 to control electrical current flowing through the coils 24.

The rotor 30 includes a hub 32 having a shaft 321 extending downward andperpendicularly from a central portion thereof, a plurality of blades 36extending radially from an outer side of the hub 32, and a magneticelement 34 adhered to an inner side of the hub 32. The shaft 321 has afixed end 322 connected with the hub 32 and a free end 323 away from thehub 32. The magnetic element 34 is annular shaped (i.e., shaped like ahollow cylinder). An inner diameter of the magnetic element 34 isslightly larger than the largest outer diameter of the stator core 22.An outer diameter of the magnetic element 34 is slightly larger than aninner diameter of the hub 32, such that the magnetic element 34 can beinterferentially fitted into the hub 32. The magnetic element 34 can bea permanent magnet, or a magnetizing magnet which is made ofnon-magnetic material magnetized to create a persistent magnetic field.

When the heat dissipation fan is assembled, the stator 20 is mountedaround the central tube 123, with the PCB 28 located on the base 121 ofthe housing 10. The rotor 30 is positioned over the stator 20, and isassembled to the stator 20 via the shaft 321 being rotatably received inthe bearing 14. An inner surface 140 of the magnetic element 34 facesand is spaced from the tapered outer surface 222 of the stator core 22,with a generally annular clearance 60 defined therebetween. A width ofthe clearance 60 increases along an axial direction from the bottom endof the stator core 22 to the top end of the stator core 22. That is, adistance between the tapered outer surface 222 of the stator core 22 andthe inner surface 140 of the magnetic element 34 increases along theaxial direction from the bottom end of the stator core 22 to the top endof the stator core 22. Thus, a magnetic attracting force formed betweenthe stator core 22 and the magnetic element 34 increases along the axialdirection from the top end of the stator core 22 to the bottom end ofthe stator core 22.

In this embodiment, along the axial direction of the stator core 22, thedistance between the top end of the stator core 22 and the magneticelement 34 is largest, and the distance between the bottom end of thestator core 22 and the magnetic element 34 is smallest, such that themagnetic attracting force formed between the top end of the stator core22 and the magnetic element 34 is smallest and the magnetic attractingforce formed between the bottom end of the stator core 22 and themagnetic element 34 is largest.

During operation of the heat dissipation fan, the rotor 30 is driven torotate by the interaction of the alternating magnetic field establishedby the coils 24 of the stator 20 and the magnetic field of the magneticelement 34 of the rotor 30. Thus rotation of the rotor 30 generates aforced airflow for cooling electronic packages, such as CPUs.

Due to the magnetic attracting force formed between the stator core 22and the magnetic element 34 decreasing along the axial direction fromthe bottom end of the stator core 22 to the top end of the stator core22, a larger magnetic attraction force acting on the magnetic element 34is generated by the bottom end of the stator core 22. When rotation ofthe rotor 30 generates an external air pressure tending to pull therotor 30 upwardly along the axial direction thereof, simultaneously, thebottom end of the stator core 22 attracts the magnetic element 34 of therotor 30 and tends to pull the rotor 30 downwardly along the axialdirection thereof. That is, the greater magnetic attraction of thebottom end of the stator core 22 counteracts the effect that theexternal air pressure would otherwise have on the rotor 30. Thus axiallyupward movement and floating of the rotor 30 during operation of theheat dissipation fan is avoided, and any problem of noise generated byfloating of the rotor 30 is correspondingly avoided.

It is to be further understood that even though numerous characteristicsand advantages have been set forth in the foregoing description ofembodiments, together with details of the structures and functions ofthe embodiments, the disclosure is illustrative only; and that changesmay be made in detail, especially in matters of shape, size, andarrangement of parts within the principles of the disclosure to the fullextent indicated by the broad general meaning of the terms in which theappended claims are expressed.

What is claimed is:
 1. A stator comprising: a stator core having an axisand comprising a plurality of yokes stacked one on the other along theaxis, wherein the stator core has a first perimeter at one end thereofthat is greater than a second perimeter at another end; two insulationframes respectively covering the one end and the other end of the statorcore; and a plurality of coils each wound around one of the twoinsulation frames and corresponding portions of the plurality of yokes;wherein each of the plurality of yokes comprises an annular plate and aplurality of arms extending outwardly from an outer periphery of theannular plate, outer edges of the plurality of arms of each yoke arelocated on a same imaginary circle which has a common center with theannular plate, so that there are a plurality of imaginary circles, andone of the imaginary circles being different from another thereof. 2.The stator of claim 1, wherein the imaginary circles are increasingalong the axis from the direction from a top end of the stator core to abottom end of the stator core.
 3. The stator of claim 1, wherein acylindrical receiving space is cooperatively defined in a centralportion of the stator core by inner peripheries of the annular plates ofthe yokes, and outer peripheries of the arms of the yokes are located asame imaginary tapered surface.
 4. The stator of claim 3, wherein thediameter of the imaginary tapered surface decreases from the one end ofthe stator core to the other end of the stator core.
 5. The stator ofclaim 1, wherein the outer size of the stator core decreases along theaxial direction thereof.